A radio frequency identification (RFID) label uses wireless data acquisition to identify and manage products. Because of a broad range of application, it is imperative to focus on ways to develop a radio frequency identification label, which enables mass production without being limited in its application. U.S. Pat. Nos. 6,262,692B1, 6,429,831, 6,275,156 and 6,094,138 have disclosed relevant radio frequency identification labels to meet its broad application.
U.S. Pat. Nos. 6,262,692B1 and 6,429,831 have disclosed a radio frequency identification label having a multi-layered structure which comprises an antenna, a chip and a circuit connecting the antenna and the chip. Referring to a prior-art radio frequency identification label 1 shown in FIG. 1, a chip 10 and an antenna 11 are encapsulated in a multi-layered structure having a plurality of laminations 12, wherein each of the laminations 12 is provided with an opening 121 for receiving the chip 10. The radio frequency identification label 1 is more cost-effective when comparing to other prior-art radio frequency identification labels as it does not require the use of expensive substrates. However, it does not meet the requirement of miniaturization as its overall thickness is increased by its multi-layer design. Furthermore, the increased thickness would also influence the flexibility of the radio frequency identification label 1, so that the radio frequency identification label 1 cannot be effectively applied to an object having an uneven surface.
Referring to FIG. 2, U.S. Pat. No. 6,275,156 has disclosed a radio frequency identification label 2 in which an antenna 20 and a radio frequency identification circuit (such as a printed circuit or a chip, not shown in the figure) are interposed between an upper lamination 21 and a lower lamination 22. Although the overall thickness can be decreased and the structure can be simplified, the height of the antenna 20 and the radio frequency identification circuit would roughen the surface of the radio frequency identification label 2, so that surface prints or other labels cannot be provided. Moreover, a gap of certain size is formed between the upper lamination 21 and the lower lamination 22. When being used in a flexible condition or applied to an object having an uneven surface, the gap can be easily expanded, so that the moisture-proof effect and the reliability of products are adversely influenced as a consequence. Additionally, the maintenance of the surface flatness and the inclusion of the upper lamination 21 and the lower lamination 22 result in an increase in the overall thickness of the radio frequency identification label 2, such that the flexibility of the label is decreased, resulting in limitation of application.
U.S. Pat. No. 6,094,138 has disclosed a radio frequency identification label, which is different from other prior-art radio frequency identification labels in terms of structures. Referring to FIG. 3, a radio frequency identification label 3 employs a flexible substrate 30 having an opening 300 penetrating therethrough, such that an integrated circuit 31 is received in the opening 300 of the substrate 30. Then, an antenna 32 is formed on the substrate 30 by spray printing. A conductive material 33 is subsequently interposed between the integrated circuit 31 and the antenna 32, so as to electrically connect the integrated circuit 31 to the antenna 32. As the integrated circuit 31 is received in the substrate 30, the overall thickness of the radio frequency identification label 3 is effectively reduced. Further, as the flexible substrate that is good in flexibility is used, the radio frequency identification label 3 can be applied to an object having an uneven surface. However, such radio frequency identification label 3 is also disadvantageous as it provides no protective or moisture-proof design. Moreover, as the conductive material 33 is interposed between the integrated circuit 31 and the antenna 32, the surface flatness cannot be easily maintained, so that surface prints or other labels cannot be provided.
Accordingly, the problem to be solved here is to provide a flexible radio frequency identification label and a method for fabricating the same, by which drawbacks occurred in the prior-art radio frequency identification labels can be eliminated, including high expenses, unreliable products due to oxidation caused by moisture, and an uneven surface.